Fatherhood lowers testosterone in men, study finds

CHICAGO (Reuters) - Fatherhood lowers testosterone levels, U.S. researchers said they have confirmed, making it easier for men to be involved in raising children.

High levels of the hormone can rev up a man's sex drive, increase risk-taking behaviors and raise the need for social dominance. Those factors can help win a mate but are poor traits when it comes to raising a baby, which requires cooperation from both parents.

"Our study shows that human fathers are biologically wired to help with the job," said Christopher Kuzawa of Northwestern University, who worked on the study published in the Proceedings of the National Academy of Sciences.

Prior studies have shown fathers tend to have lower testosterone than men who have no children but it was not clear whether fatherhood was the cause or that men with lower testosterone were more likely to become fathers.

The Northwestern study tried to answer that question by following a group of more than 600 men from the Philippines over five years. The men were not fathers at the start of the study.

The team saw clearly that right after the men became fathers, their testosterone levels dropped, at least for a short time.

"It's not the case that men with lower testosterone are simply more likely to become fathers," Lee Gettler of Northwestern University, who worked on the study, said in a statement.

"On the contrary, the men who started with high testosterone were more likely to become fathers, but once they did, their testosterone went down substantially."
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